WPF/Silverlight Data Binding Tip: FallbackValue

June 25, 2011

Consider the following piece of XAML (part of an Image Viewer application), that wants to set the Window title (in WPF) based on the currently loaded image file: Title="{Binding ImagePath, StringFormat=Image Viewer ({0})}" This assumes that a DataContext exists, and exposes a property named ImagePath. This works well if such an object actually exists. But what happens when the application starts up and there is no image loaded yet, meaning the DataContext remains null? The Title would show nothing, because the binding fails. How can we fix that? One...
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GetShellWindow vs. GetDesktopWindow

June 18, 2011

In his post about running a process as a standard user from an elevated process, Aaron Margosis uses a technique that gets the access token of the shell process (typically explorer.exe) and uses that token to launch the new process (Sasha Goldshtein also blogged about that). The first thing his code does is try to locate the shell process id. One way is to look for “explorer.exe” in the list of processes, but that’s a bit limiting, as there may be a different shell, or it may have been renamed for whatever reason. His code calls GetShellWindow to...
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A ‘Proper’ WeakReference Class

June 4, 2011

The WeakReference class that exists since .NET 1.0 can be used to wrap an object while not being the one keeping it alive. This may be useful in an “Observer” pattern scenario, where a client registers for some notification, but “forgets” to unregister. That means that with a normal reference, even if the client is no longer needed, it keeps getting notifications because the server object keeps a strong reference to the client. Here’s a simple example: class BasicSubject { ...
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